Wood burning fireplaces in a home have long been the source of both heat for warming of the house and as an attractive and appealing object to visually observe. Entire room arrangements are commonly focused on an open fireplace to permit the enjoyment of the warmth and enchantment of the burning wood within the fireplace.
Unfortunately, the burning of wood in a fireplace presents the problems of obnoxious smoke and soot, and of the inconveniences associated with keeping the fireplace area clean and the acquiring, storage and transport of the wood for burning.
Gas burning heaters or fireplace inserts (hereinafter referred to at times collectively as "insert" or "fireplace insert") which include artificial logs have become very popular in American households as a substitute for burning of wood in the fireplace. These inserts commonly burn natural gas or propane and are clean and convenient to operate. To their distraction, these inserts heretofore have not been capable of realistically simulating burning wood logs. Further, the cost of construction of the fireplace itself is not diminished by reason of one using a gas-burning fireplace insert in that the inserts frequently require a proper vent to the outside of the house to exhaust carbon monoxide combustion products from the burning gas. More recently, it has become acceptable to construct non-vented fireplaces, but only if the carbon monoxide level of the burning gas does not exceed 200 ppm and if the total BTU output of the insert is not greater than 40,000 BTU. These limitations on the level of carbon monoxide and total BTU output generated by the burning gas severely restricts the manner of operation of gas-burning inserts. For example, the most efficient burning of natural gas or propane, hence the least carbon monoxide produced, occurs when there is a proper (i.e. stoichiometric) mixture of air, or other source of oxygen, and gas. The flame produced under these conditions of combustion is characteristically blue in color. Yellow tips to the flames are pleasing to observe, but they indicate oxygen deficiency and generation of carbon monoxide. Further, in order to maintain the level of carbon monoxide at or below the permissible level for a non-vented fireplace, as well as limit the total BTU output of the insert, one is limited as to the quantity of gas made available for combustion. The use of multiple burners in the insert compounds the problems facing a designer of these inserts, particularly where it is desired to provide for control over the rate of combustion to selectively adjust the BTU output downwardly from a maximum, i.e. to select "low", "medium" and "high" heat outputs from the insert.
Attempts to enhance the flame colors have included various techniques, such as use of logs having a coating thereon which alters the color of a flame where it contacts the coated log. This type of practice is not cost effective because of the initial cost of the coatings material and its application to the logs, and because the coating commonly is fugitive.
In accordance with the;present invention there is provided a gas-burning fireplace insert which may be employed in a nonvented fireplace and which effectively simulates burning wood logs and provides the aesthetically pleasing and entrancing appearance of the flames associated with burning wood logs.
It therefore is an object of the present invention to provide an improved gas-burning fireplace insert.
It is another object to provide a non-vented gas-burning fireplace insert.
It is another object to provide a gas-burning fireplace insert which employs tiered artificial logs and selected colored flames associated with each tier.
It is another object of the present invention to provide an insert having multiple burners which have characteristically unique flame patterns and/or color.
It is another object of the present invention to provide an insert having a novel gas and/or combustion air distribution system.
It is another object of the present invention to provide a gas-burning insert having multiple burners and selective control over the total heat output of the burners to a value less than about 40,000 BTU.
It is another object of the present invention to provide a gas-burning insert in which there is generated less than about 200 pm carbon monoxide.